Method and apparatus for automatically counterbalancing pumping apparatus on oil wells



prll 9, 1940. w E sAxE 2,196,816

METHOD AND APPARATUS EUR AUTOMATICALLY COUNTERBALANGING PUMPINGAPPARATUS 0N OIL WELLS Filed Spt; VE5, 1938 3 Shee'ts-Sheet 1 FOI? THEF/RM A rroR/vgsns..

pfll 9, 1940. W E, SAXE 2,196,816

METHOD AND APPARATUS FOR AUTOMATICALLY COUNTERBALANCING PUMPINGAPPARATUS ON OIL WELLS Filed Sept. 6, 1938 3 Sheets-Sheet 2 HAR/m,K/EcH, ,Fosr #ARR/s FOR THE F/RM A Tron/vins.

AP 9, l940- w. E. sAxE .2,196,816

METHOD AND APPARATUS FOR AUTOMATICALLY COUNTERBALANGING PUMPINGAPPARATUS 0N OIL WELLS Filed Sept. 6, 1938 3 Sheets-Sheet 3 /NVENTORM/Az. 75,1? E. 4x5

HAR/ws K/ECH Fos 7E ,IPR/5 FOR THE FIRM A o RNE Ks.

Patented Apr. 9, 1940 UNITED STATES METHOD Ann APPARATUS FOR AUTO-MATICALLY COUNTERBALANCING PUMP- ING APPARATUS N OIL WELLS Walter E.Saxe, Alhambra, Calif. Application September 6, 1938, Serial No. 228,536

22 Claims.

My invention relates to a method and apparatus for securing automaticcounterbalancing, and particularly to a method and apparatusforautomatically providing correct counterbalance for a reciprocatingmember which is driven by a rotating shaft and, which if notcounterbalanced, subjects the rotating shaft to unequal loads during thetwo oppositely directed strokes.

My invention finds particular utility in the automatic counterbalancingof pumping apparatus for oil wells, and an embodiment of the apparatusvof my invention and apparatus capable of performing the method of myinvention will be described in connection with such use, it beingunderstood, however, that my invention is not limited to such use.

In oil well pumping apparatus it is customary to employ a prime moverfor rotating a shaft and to translate the rotary movement of such shaftto the reciprocating movement of a pump plunger through a crank arm, apitman, and a walking beam. When the crank arm, in its rotation, isnearly vertical, the component of its movement parallel to the directionof travel of the walking beam and the pump plunger is relatively'small,and therefore the load on the prime mover when the crank is in thisposition is also relatively small. On the other hand, 'when the crankarm is near either of its horizontal positions, it has a relativelylarge component of its movement parallel to the direction of travel ofthe walking beam and the pump plunger, and the load on the prime ,moveris then most inuenced by the load on the walking beam. If nocounterbalance is' employed, it is evident that on the upstroke of thestringof sucker rods, when the crank arm is horizontal, the prime moveris subjected to itsI greatest load, being required at that time to liftwith greatest velocity the walking beam, the

string of sucker rods, and all of the liquid being elevated in the welltubing; while on the downstroke, the walking beam and string of suckerrods fall by gravity, subjecting the prime mover to little or no load. l

In my Patent No. 2,122,871, I disclose a method and apparatus forcounterbalancing such an oil well pumping apparatus wherein airiscompressed on the downward stroke of the walking beam and energy is thusstored to assist the prime mover on the upward stroke. By properadjustment of that apparatus, I am able to make the maximum load on theprime mover during the downward stroke equal to the maximum load on theprime mover during the upward stroke, whereby increased efficiency andlonger life of4 the pumping apparatus result.- or bringing intoconsideration the time element, I may adjust that apparatus to make thework done by the prime mover during the downward stroke equal `to thework done by the prime mover during the upward stroke 5 for the samepurpose of increasing eciency.

I have found, however, that in the caseof many wells, the load duringthe upstroke of the sucker rod` does not remain constant but may varygradually and, over a period of hours, may

bec'onsiderably altered. This change may come about through operation ofvarious factors. The fraction of water contained in the oil may change,resulting in a heavier column of liquid tobe raised; or the fraction ofgas contained in the oil may change, resulting in a lighter column ofliquid. Moreover, in those wells situated adjacent the ocean, the wellpressure and the load on the sucker rod are found to change with thetide. In the case of installations of this kind, it is desirable to varythe counterbalancing force as the load on the sucker rod varies, to makethe loads on the prime mover equal during the upward and.l downwardstrokes of the sucker rod. To do this ordinarily requires closeattendance to the apparatus, which is desirable to avoid. y

It is an object of this invention, therefore, to provide a methodandapparatu's for automatically providi'ng-a counterbalancing forcewhich shall result either in the maximum prime mover load existingduring the `downward or return stroke oi the sucker rod beingsubstantially equal to the maximum prime mover load existingl during theupward or pumping stroke of the sucker rod vor in the work performed bythe prime mover during the downward or return stroke of the sucker rodbeing substantially equal to the work performed by the prime moverduring. the upward or pumping stroke of the sucker rod.

It is/also an object of the invention to provide *40 a method andapparatus for automatically making the loads uponthe prime moversubstantially equal' when the crank arm is moving upwardly through ahorizontal position and when it is moving downwardly through ahorizontal position.

Another object of-my invention is to provide a method and apparatuswhereby the prime mover is required to compress a gas during that strokeof the pump plunger in which the prime mover is normally subjected toits lesser load, and the gas is expanded during that stroke of the pumpplunger in which the prime mover is normally subjected to its greaterload, and f whereby the pressure to which the gas is com- '55 pressed isautomatically regulated to equalize either the maximum loads upon theprime mover or the work done by the prime mover during the twooppositely directed strokes of the pump plunger.

More specically, it is an object of the invention to provide in acounterbalancing apparatus for oil wells, wherein gas is compressed onthe downward stroke of the sucker rod to effect counterbalancing, meansfor automatically regulating the pressure of the gas in response to theload to be counterbalanced in such manneras to equalize either themaximum loads upon the prime mover or the work done by the prime moverduring the two oppositely directed strokes of the pump plunger.

Another object is to provide in oil well pumping and counterbalancingapparatus of the character above described, a connection between thecrank arm and walking beam which is of variable length dependent uponthe load transmitted by this connection, and means for regulating thecounterbalancing force in response to the change in length of theconnection.

A further object inA one practice of my invention is to provideapparatus which weighs or measures the maximum loads to which the primemover is subjected on both the upward and downward strokes of the pumpplunger and adjusts the counterbalancing force in response to therelative loads on the two oppositely directed strokes; and in anotherpractice of my invention it is my object to provide apparatus whichmeasures the work done by the prime mover on the upward and downwardstrokes respectively of the pump plunger and adjusts thecounterbalancing force in response to the relative amount of work doneon the two oppositely directed strokes.

Another object is to provide apparatus which measures the torquedemanded of the source of motive power and adjusts the counterbalancingforce to equalize the maximum torque demanded during the two oppositelydirected strokes of the pump plunger.

Still another object oi' the invention is to provide automaticcounterbalancing apparatus which shall require a minimum of attention.shall be efcient in operation, and shall be of long life.

These and other apparent objects I attain in a manner which will beclear from a consideration of the following description taken inconnection with the accompanying drawings, of which:

Fig. 1 is an elevational view of one form of my automaticcounterbalancing apparatus, shown partly in section, as applied topumping apparatus for a well.

Fig. 2 is a side view of a part of the regulatingr means of theapparatus of Fig. 1.

Fig. 3 is an elevational view of an alternative form of my automaticcounterbalancing apparatus.

Fig. 4 is a sectional view of a part of the apparatus of Fig. 3 takenalong the line l-4, as indicated.

Fig. 5 is an elevational view of an alternative form of my automaticcounterbalancing apparatus.

Fig. 6 is a side view of a part of the regulating means of the apparatusoi' Fig. 5.

Fig. 7 is an end view of a portion of the apparatus of Fig. 5, asindicated by the arrow 'I.

Fig. 8 is a partial sectional view ofthe apparatus of Fig. 5, takenalong the line 8-8 of Fig. 5.

Fig. 9 is a side view-of one of the pressure regulating valves shown inFig. 8.

Fig. 10 is an elevational view of an alternative form of my automaticcounterbalancing apparatus.

Fig. 11 is an end view of a portion of the apparatus of Fig. 10.

Fig. 12 is a sectional view of one of the pressure regulating valves ofFig. 8, taken along the line I2|2, as indicated.

Fig; 13 is a sectional view of the pressure regulating valve shown inFig. l2, taken along the line I3---I3.v

Fig. 14 is a sectional view of one of the pressure regulating valves ofthe apparatus of Fig. 5, taken along the line Il-Il.

Fig. 15 is a sectional view of part of the pressure regulatingmeans ofthe apparatus of Fig. 3, taken along the line I5-I5, as shown.

My invention is illustrated as applied to the pumping apparatus for anoil well I5 extending downwardly into the earth I6. The well I5 has acasing I1 and a pump tubing I8 in the lower end of which a pump plungerI9 is reciprocated by a string of sucker rods 20. The sucker rods extendupwardly through the pump tubing to above the surface of the earth andare attached by suitable means such as a cable to the working end of awalking beam 2| the other end of the walking beam preferably beingmounted ,upon a pivot 22 carried by a tulcrum frame 23.

This assembly is arranged in such a manner that rocking ofthe'walking'beam results in reciprocation o1' the pump plunger I9throughout a pumping cycle comprising an upwardly directed pumpingstroke and a downwardly directed return stroke. The fulcrum frame 23 andthe remainder of the pumping and counterbalancing apparatus arepreferably mounted on an underframe 2l carried on a foundation 25. Inthe form of pumping apparatus illustrated in the drawings, a source ofmotive power, or prime mover 28, drives a relatively large sprocket 21through a chain 28, which in turn drives a sprocket wheel 29 through achain 3U. Connected with the wheel 29 for rotation about a fixed axis 3Iis a crank arm 32. Attached to the crank arm 32 and in operativeconnection with the walking beam 2i is a pitman 33, the whole apparatusbeing adapted to raise and lower the walking beam once for everyrevolution of the crank arm 32.

Assume that the crank arm 32 rotates in the direction indicated by thearrow in Fig. l. As previously explained, the prime mover 26 willencounter the greatest load when the crank is in the horizontal positionon the upstroke ifno counterbalance is employed. At this time thewalking beam 2|, the string of sucker rods 2D, the pump plunger I9, andthe column of uid in the tubing I8 are all being elevated. As in myissued patent, above-mentioned, I preferably counterbalance the pumpingapparatus by providing an apparatus which includes a cylinder 40 securedat its lower end to a housing 4I with which it freely communicates.Reciprocable within the cylinder l0 is a piston 42 having a connectingrod Il pivotally connected thereto. The connecting rod 43 is plvoted atits upper end to the walking beam 2l at a point which is preferably nearthe point of connection of the pitman 33.

The rod 4l preferably carries a hood 44 which moves therewith and servesas a protective cover for the cylinder 40. The housing 4I normallycommunicates with a compression and `expansion chamber 45 provided witha valved supply pipe 46 for the introduction of liquid to the chamber45, the housing 4|, and cylinder 46. The chamber 45 is preferablynormally'in communication with a relatively large additional chamber 41through a pipe 49 and valve 49. The valve 49 and a valve 50 between thecylinder 40 and the chamber 45 are .ordinarily not closed unless thewalking beam is to be disconnected from the sucker rod, or the variousunits of the apparatus are to be isolated for some other reason.

Normally a liquid 39, preferably oil, lls the housing 4|, is in contactwith the piston 42, and

has a surface within the chamber 4 5 in contact with a gas, preferablyair, under pressure, which fills the remaining space in the chamber 45and the downward stroke of the walking beam which the chamber 41. Thechambers 45 and 41, housing 4|, and cylinder 40 thus constitute agas-containing chamber closed by the movable piston 42.

In normal operation, as the walking beam is brought down, the piston 42forces liquid out of the chamber 48 and into the chamber 45, compressingthe gas in the chambers 45 and 41 and requiring the prime mover to exerta torque on is determined by the dimensions'of the gas space,

the stroke of the piston, and the initial pressure of the gas in thecompression space. The use of a relatively large chamber 41, providing alargecompression space, results in a relatively small change in gasvolume due to movement of the piston 42, and therefore in a relativelysmall change in gas pressure throughout the, cycle of movement of thepiston 42. Under these conditions it will be evident that the greatesttorque required of the prime mover in compressing the gas will beencountered -When the crank arm 32- is in nearly a horizontal positionon the downward stroke, as previously explained. On the upward strokethe gas in the chambers and 41 acts upon the piston 42 to help raise thewalking beam, at 'the same time expanding to its original volume.- Ipreferably automatically control the gas pressure in the chambers 45 and41 to result -in equal maximum torques required of the prime moverduring the upward and downward strokes of the walking beam; or in equaltorques at certain stages in the upward and downward strokes, as whenthe crank arm 32 is in horizontal position on the upward stroke and inhorizontal position on the downward stroke. The -maximum torquesrequired of the prime mover on the upward and downward strokes of thewalking beam will be equal when the force exerted on the piston 42 issuch that the moment of this force about the pivot axis 22 isapproximately equal to the moment of the forces of gravity on thewalking beam 2|, the string of sucker rods, the pump plunger, andone-half of the liquid being elevatedy in the tubing |8. The apparatusof my invention is adapted to automatically regulate the pressure of gasin the chambers 45 and 41 to automatically bring about and maintainequality of .l Y, y 3 on the walking beam 2|' is a cyunaer sl sued withliquid 52, in which cylinder is a movable piston 53 on a piston rod 54which projects from -both ends of the cylinder 5|. I'he bottom of thepiston rod'54 is pivotally connected to the pit-l lower compartment andinto the upper one. The lever 55 is pivotally supported on an arm 60which in turn is pivotally supported on the walking beam 2|. The end ofthe'lever 55 opposite to that'which connects with the piston rod 54 ispivotally connected to a rod 6| of adjustable length which connects withthe regulating means.

In the apparatus, as best illustrated in Fig 2, the lower end of the rod6| is pivotally connected to an arm 62 which pivots about an axis 63.Another member 64 is also mounted to pivot about the axis 63 and carriesa sprocket wheel 65 and two flange portions angularly spaced apart andpositioned in the path of the arm 62 as it is rocked by movement of thewalking beam. Suitable adjustment means are 4provided which may take theform of screws 68 and'69 which are normally so adjusted that the angularspacing between them less the angular width of the lever 62 isapproximately equal to the angle through which the arm 62 is movedduring a stroke of the walking beam 2| if the piston 53 remainsstationary relative to the walking beam. By this means the arm 62 ispermitted to move through an angle characteristicv 'of normal torque'and correct counterbalance conditions without engaging the member 64 ateither end of its stroke.

Rotation of the member 64 is adapted to change the adjustment ofpressure regulating valves 10 and 1I by reason of the connection of achain 12 with the sprocket wheel 65 -and-a sprocket wheel 13 of thevalve 1U, and the connectionV of a chain 14 with sprocket Wheels 15 and16 of the valves 10 and 1|, respectively. The valve 10 is preferablyconnected with a high pressure gas reservoir 11 through a conduit 18,and through a conduit 19 with the conduit 4'8 connecting with thechambers 45 and 41, the valve 18 being adapted to permit gasv to ow fromthe reservoir 11 into the chambers45'and 41 to-raise the pressuretherein until it reaches an equilibrium value determined by theadjustment of the valve 10.` The pressure of gas in the reservoir 11 maybe maintained at a suitably high value above that in the chambers 45 and41 by any suitable means, such as an air compressor, connected to thereservoir 11 through the conduit 38.

The valve 10 may be constructed as shown in has one side closed by aflexible diaphragm 82 which is clamped between the housing 8l] and 1 amember 83. A hollow portion 84 extends inwardly from the housing 8|!into the chamber 8| and is formed with a valve passage 85 connecting a4passage 86 with the chamber 8|. The

passage 86 is in communication with the conduit 18, and the chamber 8|is in communication with v the conduit 19. Carried on the diaphragm 82is a valve 81 which is adapted to close the valve passage 85 by actionupon the diaphragm 82 of air pressure within the chamber8l. A spring 88acts upon the diaphragm 82 tending to lift the valve 81 from its seat.and is compressed between the diaphragm and the end of a screw 89 whichis in threaded engagement with the member 83 and its attached to thesprocket 15. The screw 89 has threads of relatively great pitch so thatit is advanced a relatively great distance toward or away from thediaphragm upon rotation through a small angle. The threads on the screw89 are cut in a direction such as to advance the screw toward thediaphragm upon clockwise rotation of the screw as viewed from thesprocket side of the valve. In the form of my apparatus illustrated inFig. 1, the screw 89 may be connected for rotation with the sprocket 13without any backlash, but since in another form of my invention,hereinafter described,it is desirable to have backlash between theseparts, I have illustrated the valve 10 in a form which permitsadjustment to provide or. eliminate backlash as desired. In this form anarm 90 is attached for rotation with the screw 89 and carries flanges ateither side through which are threaded adjusting screws 9|, which areadapted to be engaged by pins 92 attached to the sprocket 13 forrotating the arm 90 and screw 89 when the sprocket 13 is rotated so asto contact one; or the other of the screws 9|. In the apparatus ofI Fig.1, the adjusting screws 9| are both adjusted to contact the respectivepins 92 so as to connect the sprocket 13 for rotation with the screw 89without backlash.

In the operation of the valve 10, it will be apparent that the valvewill remain open, permitting gas to flow from the high pressurereservoir 11 into the chambers 45 and 41 until the pressure in thechamber 8|, which is equal to that in u the chambers 4'5 and 41, becomesgreat enough to force the diaphragm 82 suiilciently far against thespring 88 to close the valve 81. The farther the screw 89 is advancedtoward the diaphragm 82, the greater must be the pressure in the chamber8| before the valve is closed. Thus, the pressure in the chambers 45 and41 is raised by rotation of the sprocket 13 in a clockwise direction asviewed from the sprocket end of the valve 10, and the equilibriumpressure, below which the valve 10 will not permit the pressure in thechambers 45 and 41 to fall, is reduced by rotation of the sprocket 13 ina counterclockwise direction.

It will be observed that the valve 10 is not adapted to reduce thepressure in the chambers' 45 and 41, but this function is performed bythe valve 1| which is connected through a conduit 95 with the gas undercompression in the chambers 45 and 41 and with the atmosphere through aconduit 98. The valve 1| has a housing 91 providing a chamber 98 withinand has one side closed by a diaphragm 99. A hollow portion provides aspace |0I within, which is in connection with the conduit 88, and has avalve passage |02 connecting with the chamber 98. A valve member |03,which is adapted to close the valve passage |02, is carried on thediaphragm 99 and is urged into closed position by action of a spring |04pressing on the diaphragm. As in the case of the valve 10. the end ofthe spring |04' is forced to or from the diaphragm by rotation of thesprocket wheel, which, in the case of the valve 1|, is designated by thenumeral 18. The construction of the valve 1| is such that when the chain14 is connected between the valves 10 and 1| as shown, rotation of thesprockets 15 and 'i8 in a clockwise direction. as viewed from thesprocket end of the valves, results in increasing the compression of thespring |04, and, conversely, rotation in a counterclockwise directiondecreases the compression of the spring |04.

lIn the operation of the valve 1|, the valve passage |02 will be open ifthe air pressure in the chamber 98 acting upon the diaphragm 99 issufficient to overcome the compression of the spring |04, and underthese circumstances air in the chambers 45 and 41 may pass out throughthe valve passage |02 to the atmosphere until the pressure has beenreduced to a value at which the spring 04 will cause the valve member|03 to seat.l It will be clear that in this manner the valve 1| willautomatically limit the pressure in the chambers 45 and 41 to a pressureequal to or below that for which the valve will open, and that byrotation of the sprocket 18 the equilibrium pressure of the valve may beraised or lowered.

'I'he valves 10 and 1| are preferably so adjusted relative to oneanother, as by the relative orientation of the sprockets 15 and 16, asto cause the valve 1| to open at a pressure somewhat higher than thepressure at which the valve 10 is adapted to close, the difference inthese two pressures preferably being about the same as, or a little morethan. the difference in air pressure within the chambers 4'5 and 41which is to be expected from the movement of the piston 42.

The operation of the apparatus of Fig. 1 can now advantageously beexplained. At the start of the pumping operation, if the piston 53 isnot located about in the middle of the cylinder it is preferably broughtto this location by opening the valve 58 and moving the piston relativeto the walking beam. If desired, the hand pump 59 may be employed forthis purpose. When the piston 53 is centrally positioned in the cylinder5|, the valve 58 is partially closed to provide only a small by-passopening for flow of liquid through the conduit 51, and the pumpingapparatus may be started. As the walking beam 2| is forced up and downby the pitman 33 acting through the piston 53 and the liquid 52contained in the cylinder 5|, the piston 53 will reciprocate slightlywithin the cylinder 5|. On the upward stroke the piston 53'will force asmall amount of liquid out of the upper compartment through the conduit51 and valve 58 into the lower compartment, the amount of liquid thustransferred depending upon the adjustment of the valve 58 and theaverage force with which the piston 53 presses upwardly upon the liquid52 during the time period of the upward stroke. On the downward stroke,the piston 53 forces a small amount of liquid out of the lowercompartment into the upper compartment through the conduit 51 andvalve.58. Thus, the piston and cylinder connection between the pitmanand walking beam measures the work done by the pitman during its twooppositely directed strokes. If the displacement of the liquid on theupward or pumping stroke is equal to the lliquid displacement on thedownward or return stroke, the piston will after each downward stroke belocated in the same position relative to the cylinder 5| and walkingbeam 2|; but, if the liquid displacement on the upward stroke is greaterthan that on the downward stroke, the piston will on each upward strokerise in the cylinder 5| more than it will fall on the downward strokeand will therefore gradually assume a higher position in the cylinder5|. If, however, the liquid displacement by the pisclsI ton on thedownward stroke is greater than that exerted on the upward stroke, thepiston will gradually shift to a lower position in the cylinder 5|.

The upward movement of the piston 53 relative to the walking beam causesthe rod 6| to be moved downwardly relative to the walking beam,resulting in a clockwise rotation of the arm 62 (as seen in Figs. 1 and2). Since the walking beam carrying the rod 6| is normally moved witheach revolution .of the crank 32 up and down through a fixed angle, thearm 62 also has a certain normal oscillation due to the movement of thewalking beam. Preferably, the screws 68 and 69 of the member 64 are soadjusted that in the normal oscillation of the arm 62 due to movement ofthe walking beam, with the piston 53 and lever 55 stationary relative tothe walking beam, the arm 62 will come nearly to but not move the screws68 and 69 at the respective ends of its stroke. When the rod 6| isdepressed relative to the walking beam, it is evident that the arm willcontact the screw 69 at the lower end of its stroke, causing clockwiserotation of the member 64 and sprocket 65, and as the rod 6| is furtherdepressed by reason of the piston 53 rising still higher in the cylinder5|, the sprocket 65 will be further rotated in proportion to themovement of the piston 53. As the sprocket 65 is rotated clockwise, thesprockets 13 and 16 of the valves 10 and 1|, respectively, Will also berotated clockwise. As previously explained, this readjustment of thevalves 16 and 1| will result in higher equilibrium pressures for the twovalves. Consequently, the valve 10 will open to permit air from the highpressure reservoir 11 to iiow into the chambers 45 and 41 until thepressure therein rises -to the new equilibrium value. This causes theforce exerted by the liquid 39 on the piston 42 to be greater on theupward stroke, which reduces the load on the pitman 33, and on thedownward stroke the pitman 33 is required to pull harder in order tocompress the air under the higher pressure. Thus, the excess of force ofthe piston 53 on the liquid 52 on the upward stroke over that on thedownward stroke is reduced by the increase in pressure of air in thechamber 45 and 41 which has taken place. Eventually the pressure of airin the chambers 45 and 41 will rise to la value at which the workperformed by the piston 53 on the liquid in the cylinder 5| is the sameon the. upward stroke as on the downward stroke, and the mean positionof the piston 53 relative to the walking beam 2| will remain the samefrom one cycle to the next. Under these conditions, the work demanded bythe pump will be correctly counterbalanced. .Y

It will be apparent that when the work demanded by the pump is reduced,the piston 53 will gradually fall relative to the walking beam, causingthe rod 6| to be elevated, and resulting in the arm 62 contacting thescrew 68 at the upper end of its stroke, thereby rotating the member 64and sprocket 65 in acounterclockwise direction. The sprockets 13 and 16will be rotated in counterclockwise direction, and the equilibriumpressures of the valves 10 and 1| will be lowered. The valve 1| will`therefore open and permit air to pass out to the atmosphere until thepressure in the chambers 45 and 41 has fallen to a value at which thevalve 1| will close. In this manner the force exerted upon the piston 42by the liquid 39 will be reduced until the force required to be exertedby the piston 53 on the liquid 52 is substantially the same during theupward and downward strokes, and the pump load is again correctlycounterbalanced.v It will be observed that, regardless of how the pumpload changes, my apparatus automatically brings about a condition ofcorrect counterbal-v IH are at their upper ends connected to oppositeends of a beam ||2 extending transverse to the walking beam 2|. In themiddle of the beam ||2 and fixed thereto is a cylinder ||3 lled withliquid ||4. Within the cylinder H3 is a movable vpiston ||5 fixed on apiston rod ||6 which `passes through suitable packing and projectsthrough both ends of the cylinder. The upper end oi the rod' ||6 ispivotally connected with the Walking beam 2| through suitable bearingmeans H1. A by-pass conduit H8. is provided connecting the liquid onopposite sides of the piston H5, and an adjustable valve ||9 is placedin the conduit |18. A pipe |20 is provided for lling the cylinder withliquid. An indicating linger |2| is carried by the piston rod ||6 andserves to indicate the position of the piston ||5 within the cylinder.

For regulating the pressure in the chambers 45 and 41, I provide an aircompressor |24, provided with suitable intake and discharge valvesandadapted to take in air from the atmosphere and compress it into thechambers 45 and 41 through a conduit |25. The compressor |24 preferablyhas a vertical cylinder mounted stationary with respect to the frame 24of the pumping apparatus, has a piston movable in the cylinder, and hasa piston rod |26 connected to the piston. The piston. rod |26 ispivotally connected to a connecting rod |21, having means |28 foradjusting its length, the connecting rod |21 being pivotally connectedto the walkingbeam 2|. The piston of the compressor I 24 will thus bereciprocated as the walking beam is moved up and down. The stroke of thepiston will remain substantially constant regardless of the position ofthe cylinder |3 relative -to the walking beam 2|,'butthe depth to whichthe piston moves in the compressor |24, and therefore the clearance ofthe compressor, will depend upon the relative position of the cylinder||3 and the walking beam. The discharge pressure of a compressor beyondwhich it will not compress is dependent upon the clearance of thecompressor, the smaller the clearance being, the higher being thepressure to which it will compress. Thus, the maximum pressureattainable in the chambers 45 and 41 is determined by the minimumclearancev allowed in the compressor |24. The normal clearance of thecompressor |24 is preferably adjusted by varying the length of the rod|21-to permit a discharge pressure which, acting through the liquid 39on-the piston 42, will provide substantially the correct degree ofcounterbalancing of the pump load normally encountered when the piston|5 is positioned in the middle of the cylinder H3.

'I'he variation 4of clearance of the compressor |24 from its normalamount may be employed to increase the air pressure in the chambers 45and 41, but to decrease the air pressure I employ a valve |30 which isstationarily mounted on a member of the frame and has an operating arm|3| projecting therefrom in the path of an upper pin |32 and a lower pin|33 adjustably mounted on the rod |21. The pins |32 and |33 arepreferably spaced apart along the rod |21 at such a. distance that inthe normal movement of the rod |21 due to oscillation of the walkingbeam 2| the pins at opposite ends of the stroke almost, but not quite,contact the arm |3|. The valve |30 may be constructed as illustrated inFig. 15. Two dished members |35 and |36 are clamped together with adiaphragm |31 between providing a chamber |38 between the diaphragm andthe member |36. Connecting with the chamber |38 is a conduit |39 whichleads to the gas under compression in the chambers 45 and 41. A valvedpassage |40 leads from the chamber |38 to the atmosphere, and is adaptedto be closed by a valve member |4| which is carried on the diaphragm |31and urged by a spring |42 into a closed position. The compression of thespring |42 is adapted to be increased by counterclockwise rotation ofthe arm |3|, as seen in Fig. 3, and to be decreased by clockwiserotation thereof, this adjustment being eiected through action of ascrew |43 attached to the arm |3|. When the pressure of air in thechambers 45 and 41, and therefore in the chamber |38, is great enough toovercome the compression of the Spring |42, the valve member |4| isunseated, permitting air to flow out of the chambers 45 and 41 until thepressure drops to a value at which the spring is able to close thevalve. By movement of the arm |3| up or down, then 'the maximum pressurepermitted in the chambers 45 and 41 may be lowered or raised. l

In the operation of the apparatus illustrated in Figs. 3 and 4,preferably the piston ||5 is first located about in the middle of thecylinder ||3. This may be accomplished by opening the valve ||9 andmoving the walking beam 2| relative to the cylinder ||3 until the pistonis in the desired position as indicated by the indicator |2|. The valve9 is then preferably closed to a point where the piston I5 moves only aslight distance within the cylinder ||3 during a stroke of the walkingbeam. If the pressure of air in the chambers 45 and 41 is such that thepump load is correctly counterbalanced, the piston 5 will move down inthe cylinder |3 a short distance on the upward stroke of the pumpplunger and up an equal distance on the downward stroke. The clearanceof the compressor |24 will remain constant at an amount which limits thedischarge pressure of the compressor to that existing in the chambers 45and 41, and the arm |3| will be unmoved by the reciprocation of the rod|21. If, however, the counterbalancing effect of the pressure in thechamber 45 is not sufcient, the piston ||5 will fall in the cylinder 3on the upward stroke more than it will rise on the downward stroke, andthe piston ||5 will gradually assume a lower and lower position in thecylinder ||3. This, in effect, shortens the pitmans and decreases theclearance in the compressor |24. The compressor therefore compresses airinto the chambers 45 and 41 to a higher pressure until a pressure isreached at which the piston ||5 no longer falls in the cylinder ||i3 andthe counterbalance is again correct for the load. Should the pump loaddecrease so as to result in the counterbalancing force being too great,the piston ||6 will rise more in the cylinder ||3 on the downward strokethan it will fall on the upward stroke, and the piston will graduallyrise in the cylinder ||3. This, in effect, lengthens the pitmans andresults iniI the pin |33 engaging the arm |3| at the end of the upwardstroke of the rod |21, causing readjustment of the valve |30 to a lowerequilibrium pressure. Air thereupon escapes from the chambers 45 and 41through the valve |30 to the atmosphere luntil the pressure on thepiston 42 is such as to result in a balance of the work performedthrough the pitmans ||0 and on their two oppositely directed strokes.When this condition of balance occurs, the valve |30 will not bedisturbed from its condition of equilibrium by reciprocation of the rod|21, and the apparatus continues to function with correctcounterbalance.

In the form of my counterbalancing apparatus illustrated in Figs. 5, 6,7, and 8, the pitman |45 is at its lower end pivotally connected to thecrank arm 32, and at its upper end to a weighing arm |46 preferably neara pivot |41 through which the weighing arm |46 is pivotally connected tothe walking beam 2|. The walking beam is pivotally supported on a pivot|48 mounted in the fulcrum frame members 23. The end of the weighing arm|46 is bifurcated to provide two semi-circular branches |49 and |50disposed in parallel planes. Located between the lower halves of thebranches |49 and |50 of the weighing arm and spring abutments |5|, whichare mounted' on the pivot |48, are springs |52, and between the upperhalves of the branches |49 and |50 and the spring abutments 5| aresprings |53 preferably identical to the springs |52. Riding on the underside of the branch |49 of the weighing arm is a roller |54 rotatablymounted on the end of a rod |55 and urged into contact with the branch|49 by a spring |56. A stop |51 on the rod |55 limits the upward travelof the rod |55, by engagement with a stationary bracket |58, to aposition wherein the roller |54 is in engagement with the branch |49when the semicircular branches |49 and |50 of the weighing arm |46 areconcentric with the pivot |48. Riding on the upper side of the branch|50 of the weighing arm is a roller |59 rotatably mounted on the end ofa rod |60 and urged into contact with the branch |50 by a spring |6|. Astop |62 on the rod |60 limits the downward travel of the rod |60, byengagement with the bracket |58, to a position wherein the roller |59 isin engagement with the branch |50 when the semicircular branches |49 and|50 of the weighing arm |46 are concentric with the pivot |48. The

lower ends of the rods |55 and |60 are pivotally connected to levers |63and |64, respectively, of a differential motion device |65 which isadapted to translate the varying reciprocation of the rods |55 and |60'into changes in adjustment of the pressure regulating Ivalves 10 and1|.

The differential motion device |65 may comprise a frame providing twospaced bearing brackets |66 having suitable bearing means in which isrotatably supported a tubular shaft |61 having an enlarged gear housingportion |68. Mounted rotatably within the tubular shaft |61 at one sideof the housing portion |68 is a shaft |69 to which is attached forrotation therewith a grooved wheel |10. Within the housing |68 andattached to the shaft |69 is abeveled gear |1|. Mounted rotatably withinthe tubular shaft |61 on the other side oi the housing portion |68 is l.shaft |12 to which is attached for rotation therewith a grooved wheel|13. Within the housing |68 and attached to the shaft |12 is a bev-Aeled gear |14. Within the housing |68 and meshing with both gears |1|and |14 are beveled gears |15 and |16 mounted rotatably on a shaft |11which is supported in the housing portion |68 of the tubular shaft |61.Al sprocket |18 is adjustably mounted on the tubular shaft |61 forrotation therewith and is in driving relation with the sprocket 13 ofthe valve 10 through a chain |19. A shoe |80 engages the, peripheralgroove of the wheel |13 and is connected by a link |8| to an arm |82 ofthe lever |63 which is-mounted to pivot about the axis of the wheel |13.The arrangement of the arm |82, link |8|, and shoe |80 is such thatrotation of the arm |82 in a counterclockwise direction results inurging the shoe |80 into closer contact with the wheel |13, wherebycontinued rotation of the arm |80 rotates the wheel |13 in the samedirection. In'

engagement with the peripheral groove of the wheel |10 is a shoe |83connected by a link |84 with the arm |85 of the lever |64. Thearrangement of the arm |85, link |84, and shoe |83 is such thatclockwise rotation of the arm |85, as viewed in Figs. 5 and 6, resultsin urging the shoe |83 into closer contact with the wheel |10, wherebycontinued rotation of the arm |85 rotates the wheel |10 in the samedirection. Brake shoes |86 and |81 are hingedly supported from the frameand are held in tight engagement with the wheels |13 and |10,respectively, by springs |88 and |89, respectively, inorder to preventrotation of the wheels'except when acted upon by the appropriate shoesin driving contact.

By reason of the above-described ydriving connections of the levers |63and |64 with the wheels |10 and |13, and the above-described gearconnections within the device |65, it will be evident that if the lever|63 is moved downwardly, the sprocket 18 is rotated counterclockwise asviewed in Fig. 5, and if the lever |64 is lifted, the sprocket |18 isIrotated in a clockwise direction, the diierential gearing enabling eachof the wheels |10 and |13 to be moved independently of the others. Theconnection of the chain |19 to the sprockets |18 and 13 causes thesprocket 13 to be moved in a direction toadjust the valve 10 to a higherequilibrium pressure in the chambers 45 and 41 when the lever |64 islifted. Since in normal operation the levers |63 and |64 are movedupwardly and downwardly through small angles as the walking beam ismoved upwardly and downwardly, resulting in oscillation of the sprocket13 through a small angle, it is desirable to move the screws 0| on thevalve 10 away from contact with the pins 02 so as to allow an angularmovement of the sprocket 13 equal to that produced during normal correctcounterbalance conditions without resulting in movement of the -arm andchange in adjustment of the valve 10. When the angular movement of thesprocket '13 is greater than normal in either direction, however, thearm 00 is engaged and moved to adjust the valve 10 and, through thesprockets` to lift the walking beam and in so doing lifts the bifurcatedend ofthe weighing arm againstk the springs |52. 'I'he roller |59 androd |60 are raised,'lifting the member |64. The oscillation of thewalking beam does not disturb the position of 'the rod |60 because thesurface of the branch |50 of the bifurcated weighing arm is y concentricwith the pivot of thel walking beam.

As the weighing arm |46 rises relative to the pivot |48, therod |55 alsorises until the weighing arm passes the position in which its bifurcatedend is concentricwith the pivot |48. At this point the rod |55 isstopped by engagement of the stop |51 with the bracket l|58 and is notmoved again until the weighing arm |46 is again lowered below itsconcentric position. On the downward stroke the pitman 45 acts throughthe weighing arm |46 to lower the walking beam and in so doing depressesthe bifurcated end of the weighing arm against the springs |53, loweringthe lever |63. The rod |60 follows the weighing arm down until it passesthe position of concentricity with the pivot |48, at which point the rod|60 is stopped by engagement of the stop |62 with the bracket |58 and isnot moved again until lifted by engagement with the weighing arm on itsupward stroke. It is apparent, then, that during each upward stroke ofthe pump plunger the rod |60 and lever |64 will b e lifted, and thewheel |10 will be rotated clockwise (in Fig. 5) by an amountproportional to the distance the bifurcated end of the weighing arm |46is raised above the position of concentricity with the pivot |48; andthat on each downward stroke the rod |55 and lever |63 are lowered, andthe wheell |13 is rotated counter-clockwise, by an amount proportionalto the distance the bifurcated end of the weighing arm is lowered belowthe position of concentricity with the pivot |48. Since the wheel |10 ismoved only when the lever |64 is raised, and the wheel |13 is moved onlywhen the lever |63 is lowered, and since the resultant rotation of thesprocket |18 is proportional tol the difference in motion of the wheels10 and difference in distances above and below the po-l sition ofconcentricity to which the weighing arm |46 is moved on the upward anddownward strokes. The resultant movement of the sprocket |18 istherefore responsive to the difference in force exerted by the pitmanduring its two oppositely directed strokes. If on each upward stroke theweighing arm |46 is raised farther from the concentric position than itis lowered below that position on the downward stroke, the wheel |10will be rotated clockwise on the upward stroke more than the' wheel 13will be rotated counterclockwise on the downward stroke, and there willbe a resultant rotation of the sprocket |18 in a clockwise direction. Ifon the downward stroke the weighing arm |46 is lowered from its centralposition more than it is raised beyond this position on the upwardstroke, there will be a resultant rotation of the sprocket |18 in acounterclockwise direction.

When the conditions are such that ,correct counterbalance exists, theforce exerted by the pitman |45 on the weighing arm |46 is the same onthe upward stroke as on the downward stroke, and the same compression ofthe springs |52 and |53 therefore results. vUnder these conditions,therefore, the rod' |60 will be lifted on the upward stroke through thesamedistance that the rod |55 will be lowered on the downward stroke,and there will be no resultant rotation of the sprocket |18. Thesprockets |18 and 13 will oscillate back and forth at each stroke, butthe arm 90 will not be engaged at either end of the oscillation, and theadjustment of the valves 10 and 1| will not be disturbed. If, however,the load changes so that the counterbalanclng force is insuicient, theweighing arm |46 will be raised more from the central position on theupward stroke than itis lowered below that position on the downwardstroke, and the sprockets |18 and 13 will be rotated more in theclockwise direction than inthe counterclockwise direction. The arm 90 ofthe valve 10i will then be rotated slightly in the clockwise directionduring each cycle, resulting in a gradual readjustment of the Valves 10and 1| toward a higher equilibrium pressure in the chambers 45 and 41,as previously described in connection with the apparatus of Fig. 1.uThis process of readjustment will be continued until the pressure in thechamber 45 becomes great enough to exert sutlicient force on the piston42 to result in a condition of correct counterbalance in which thesprings |52 and |53 are compressed equally on the upward and downwardstrokes, respectively, whereupon no further resultant rotation of thesprockets |18 and 13 results, and the valves 10 and 1| are not furtherchanged. When the pump load decreases so as to require lesscounterbalancing force, it will be evident that the rod |55 will belowered more on each downward stroke than the rod |60 will be raised oneach upward stroke, and there will be a resultant rotation of thesprockets |18 and 13 in a counterclockwise direction which willgradually effect a readjustment of the valves 10 and 1| to decrease thepressure in the chambers 45 and 41 until a condition is reached in whichthe bifurcated end of the weighing arm |46 is raised on the upwardstroke above the pivot |48 as much as it is lowered below the pivot onthe downward stroke. When this condition of correct counterbalance isreached, no further adjustment of the valves 10 and 1| takes place untilthe pump load further changes.

In the form of my apparatus illustrated in Figs. 10 and 11, Ipreferably, although not necessarily, employas a prime mover an electricmotor 200 the frame of which is pivotally mounted in bearings 20| andresisted in its rotation by a spring 202 located between a stationaryspring abutment 203 and an arm 204 attached to the motor frame. Themotor 200 drives the pumping apparatus through the chain 28, sprocket21, chain 30, and sprocket 29, as in the other forms of my apparatus. Apitman 205 is pivotally attached at one end to the crank arm 32 and atthe other end is pivotally attached directly to the walking beam 2|.Supported on a pedestal 206 on the under frame 24 is a differentialmotion device 201 simi lar to that illustrated in Fig. 8 except for thefollowing diierences which relate to the means for moving the wheels |10and |13. A shoe 208 is in contact with the top of the wheel |10 and isconnected to an arm 209 through a link 2|0. The arm 209 is pivoted aboutthe axis of the wheel |10 and is drawn down by a spring 2|| against astationary stop 2|2. The arrangement of the shoe 208, link 2|0, and arm209 is such that rotation of the arm 209 in a clockwise direction, asviewed in Fig. 10, results in urging the shoe 208 into closer contactwith the wheel |10 and rotation of the wheel |10 in a clockwisedirection. In contact with the wheel |13 ls a shoe 2|3 connected by alink 2|4 to an arm 2|5 which is pivoted about the axis of the wheel |13and drawn up by a spring 2|6 against a stationary stop 2|1. Thearrangement of the shoe 2|3, link 2| 4, and arm 2|5 is such thatcounterclockwise rotation of the arm 2 l 5 results in urging the shoe2|3 into closer contact with the wheel |13 and rotation of the wheel |13in a counterclockwise direction. The sprocket |18 of the differentialdevice, which is moved in response to the differential motion of thewheels |10 and |13, is connected to the sprocket 13 of the valve 10 bythe chain |19, and the valves 10 and 1| are, as in the previouslydescribed apparatus, connected by the chain 14.

An arm 220 is pivotally attached preferably to the top of the frame ofthe motor 200 and projects toward the differential motion device 201.The end 22| of the arm 220 extends transversely a sufficient distance toengage either the arm 209 `or the arm 2 I5 if it is located at asuitable vertical elevation and is moved toward the right in Fig. 10.The end 22| is preferably rounded at its top and bottom edges to permitit to readily move into positions opposite the arms 209 and 2|5 whenthese arms lie against their respective stops. A cable 222 is connectedto the pitman 205, passes over a pulley 223 which is attached to thefulcrum frame 23, and connects to the end 22| of the arm 220 in suchmanner that when the crank arm 32 is rotating in the counterclockwisedirection as seen in Fig. 10, and as indicated by the arrow, and whenthe crank arm 32 is in the horizontal position on its upward stroke, thearm 220 is positioned opposite the arm 209, and when the crank arm 32 isin the Vhorizontal position on its downward stroke, the arm 220 ispositioned opposite the arm 2 I5.

In the operation of the apparatus of Fig. 10, the torque of the motor200 will be found to vary continually being greatest at the times whenthe crank arm 32 is in an approximately horizontal position. Since themotor armature is rotating in a counterclockwise direction in order toturn the crank arm 32 in a counterclockwise direction, the frame of themotor 200 will tend to turn in a clockwise direction and will beresisted by the spring 202 bearing on the arm 204. As the torque of themotor 200 varies, the frame of the motor will therefore assume variousangu- .lar positions determined by the torque and by the resistance ofthe spring 202. As the frame of the motor 200 turns clockwise inresponse to increasing torque, the arm 220 will be moved toward thedifferential motion device 201. Since the torque is greatest when thearm 220 is opposite either the arm 209 or the arm 2|5, it is evidentthat at these times the arm 220 will be forced farthest to the right.The arrangement and dimensions are such that the arm 220 in itsuppermost position engages the arm 209 and in its lowermost positionengages the arm 2 |5 under any\condition of torque greater than thelowest torque to be expected at these positions. During the pumpingoperation, then, the arm 220, on the downward stroke of the walkingbeam, engages the arm 2|5, moves' it to the right, turning the wheel |13counterclockwise, and withdraws as it proceeds upwardly, and, on theupward stroke of the walking beam, engages the arm 209, forcing it tothe right, turning the Wheel |10 in a clockwise direction, and againwithdraws as it moves downwardly. After each engagement by the arm 220,the arms 209 and 2|5 are returned by the springs 2I| and 2|6,respectively, against the stops 2|2 and 2 l1, respectively, where theyare in position to again be engaged bythe arm 220. It will be apparent,then, that the sprockets |18 and 13 will lbe rotated in acounterclockwise direction at the midpoint of each downward stroke ofthe walking beam and will be rotated back in a clockwise direction atthe midpoint of each up" ward stroke of the walking beam, and that theangles through which the sprockets move will be v proportional to themaximum torque of the motor during the twostrokes. The screws 9| von thearm 90 of the valve 10 are preferably set away from the pins 92 sothatwith a normal torque and a condition of correct"counterbalance the pins92v do `not engage the screws 9| and thev sprocket 13 oscillates backand forth at each` stroke without moving the arm 90 controlling thevalve 10.

When a condition of correctcounterbalance exists, the maximum torqueexerted by the motor 200 is the same on the upward stroke as .on thedownward stroke, and the arm 209 will be moved through the same angle ina clockwise direction.

as the arm 2| 5 is moved in a counterclockwise direction. Thecontrolling arm 90 of the valve 10j will therefore remain unmoved, andthepressure in' the chamber 45 will remain unchanged.

If, however, the pump load increases so as to make the counterbalancingforce insumcient, the torque exerted on each upward stroke will begreater than' that exerted on each downward stroke, and the sprocket 13will be turned c lockwise during each pumping cycle more than it` willbe'turned counterclockwise, with the result that the :arm 90 of thevalve 10 will at each upward stroke be advanced through a small angle inthe clockwise direction, causing readjustment of the valves 1|! and 1|.to a higher equilibrium pressure. This gradual readjustment of. thevalves 10 and '1| will continue until the pressure in the chamber- 'isincreased suiciently to equalize the maximumtorque exertedv by themotor200 on the two oppositely directed strokes of the pump plunger. Shouldthe pump load decrease soas to make the counterbalancing force toogreat, it will be clear that the sprocket 13 will be rotated fartherduring each downward.

stroke than during each upward stroke, and the valves l0 and 1| willgradually undergo readjustment to a lower equilibrium pressure until thepressure in the chamber l5 has dropped to a value at which the maximumtorque'of the motor 200 is the same on the .upward and down-` wardstrokes of the walking beam'and correct counterbalance again exists.

In summary, it may be noted that in the form .of my invention shown inFigs. 1 and 2 and again'in the form of the invention shown in Figs.

3 and 4 the amount of liquid displaced and the means forcounterbalancing pressure varies with y both the force and thetimeinterval during which the force is eiective on one of the strokes .ofthe apparatus. The fluid displacement ona stroke,

then, varies with the work performed by the `prime, mover on a'stroke.On the other hand,

in the form of my invention illustrated in Figs.

5 to 8 and again in the form illustrated in Figs.

l0 and 11, the maximum forcel exerted by the prime mover on 'therespective strokes of the apparatus is measured mechanically withoutregard tothe time duration of the force, and the automatic arrangementtends to -establish. a condition in which the maximum force exerted bythe primexmover on the one stroke of the apparatus is equal to themaximum force exerted by the prime mover on the other stroke of theapparatus.

At the heart of my invention is the concept 5 of selecting or providingsome means in the` apparatus responsive to the" loads imposed on`theprime mover, measuring the responseot that means to the loadsimposed'fon the prime mover on the working strokes of the apparatus,measuring the response .of that means to the loads imposed'on the primemover on the return strokes of the apparatus, and then read-justing the'counterbalancing means as required in proportion to the difference linsaid response during the two opposite strokes of the apparatus to makesaidresponses substantially equal. In -the iirst two forms of myinvention illustrated in'Flgs. 1 to 4'- the means. that responds to theloads imposed onvthe prime mover isa hydraulic'arrangement. In the othertwo forms of my invention the means that responds to variations in theloads imposed Y on the prime mover is of mechanical character. It is tobe noted'that the responsive means may be located in various parts ofthe apparatus and may be functionally associated with various elementsof the apparatus. Thus, the responsive means may be incorporatedsomewherein the chain4 of operative connections between the ber througha power stroke' and a return stroke, and including a driving element,the combina-- tion of: means for applying a counterbalancing force to amoving part of said apparatusv for' counterbalancing the reciprocatingparts thereof, whereby the loads on said driving element duringthe'power and return strokes of said member are substantially equalized;and means responsive to the diierence in loads during tl'fie-oppositely/directed strokes 'of said member adapted upon relativeincrease in load during the power stroke to increase saidcounterbalancing force, an'd adapted upon relative decrease in loadduring the power stroke to decrease said counterbalancing force. y

' 2. In an apparatusV for reciprocating a pump plunger, the combinationof: means for applying acounterbala'ncing force to a moving part of said.primevmover and the pump in the well, or, as in `-the'form of theinvention shown in Figs.

apparatus for counterbalancing the reciprocat-` ing parts thereof; meansfor increasing said counterbalancing force;v means for decreasing saidcounterbalancing force; and means responsive to the difference in loadson a moving part of said apparatus during the pumping and returnstrokes'of said plunger adapted upon rela- .tive increase in load duringthe pumping stroke to bring into operation said means for increasingsaid counterbalancing force, and adapted upon relative decrease in loadduring the pumping stroke to bring into operation said means for'decreasing said counterbalancing force.

3. In apparatus for reciprocating .la pump` plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke, the combinationof: means for applying a counterbalancing force to a moving part of saidapparatus for counterbalancing the reciprocating parts thereof; andmeans responsive to the difference in loads on a moving part of saidapparatus during the pumping and return strokes of said plungerand'acting during a portion oi each pumping cycle, said last mentionedmeans being adapted upon relative increase in load during the pumpingstroke to increase said counterbalancing force, and adapted uponrelative decrease vin load during the pumping stroke to decrease saidcounterbalancing force.`

4. In apparatus for reciprocating a pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke, said apparatusincluding a motive power source, the combination of: vmeans for applyinga counterbalancing force to a moving part of said apparatus forcounterbalancing the reciprocating parts thereof; and means responsiveto the difference in torque exerted by said motive power source duringthe pumping and return strokes of said plunger and acting during aportion o each pumping cycle, said last mentioned means being adaptedupon relative increase in load during the pumping stroke to increasesaid counterbalancing force, and acting upon relative decrease in loadduring the pumping stroke to decrease said counterbalancing force.

5. In an apparatus for reciprocating a pump plunger including a rotatingcrank, a walking beam, and connecting means extending from said walkingbeam to said pump plunger Whereby the rocking of said Walking beam movessaid pump plunger, the combination of: a pitman connected to said crank;means for applying a counterbalancing force to said walking beam forcounterbalancing the reciprocating parts of said apparatus; adjustablemeans for controlling the amount of said counterbalancing force; andmeans interposed between said pitman and said walking beam responsive tothe diierence in force exerted by said pitman during the pumping andreturn strokes of said pump plunger adapted upon relative increase ofthe iorce exerted by said pitman during the pumping stroke of said pumpplunger to adjust said controlling means to effect a greatercounterbalancing foi-ce, and adapted upon relative decrease of the forceexerted by said pitman during the pumping stroke of said pump plunger toadjust said controlling means to effect a smaller counterbalancingforce.

6. In an apparatus for reciprocating a pump plunger including a rotatingcrank, a walking beam, and connecting means extending from said walkingbeam and to said pump plunger whereby the rocking of said walking beamlmoves said pump plunger through a pumping cycle comprising pumping andreturn strokes, the combination of: a pitman connected to said crank;means for applying a counterbalancing force to said walking beam forcounterbalancing the reciprocating parts of said apparatus; means forincreasing said counterbalancing force; means for decreas ing saidcounterbalancing force; and means interposed between said pitman andsaid walking beam responsive to the difference in force exerted by saidpitxnan during the pumping and return strokes of said plunger and actingduring a portion of each pumping cycle, adapted upon relative increasein force exerted by said pitman during the pumping stroke of saidplunger to Vbring into operation said means for increasing saidcounterbalancing force, and adapted upon relative decrease in forceexerted by said pitman during the return stroke to bring into operationsaid means for decreasing said counterbalancing force, whereby theamount of said counterbalancing force is automatically adjusted to sucha value that the force exerted by said pitman is substantially equalduring the pumping and return strokes of said plungen 7. In an apparatusfor reciprocating a pump plunger, the combination of; means for applyinga counterbalancing force to amoving part of said apparatus forcounterbalancing the reciprocating parts thereof, said means including ahuid-tight chamber containing gas under pressure, and a piston closingsaid chamber and connected to a moving part oi said apparatus in suchmanner that said gas is expanded and energy delivered to said pistonduring the pumping stroke of said plunger and the gas is compressed bysaid piston during the return stroke ofsaid plunger; and meansresponsive to the difierence in loads on a moving part of said apparatusduring the pumping and return strokes of said plunger adapted uponrelative increase in load during the pumping stroke to increase thepressure of said gas, and adapted upon relative decrease in load duringthe pumping stroke to decrease the pressure of said gas.

8. In apparatus for reciprocating a pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke, the combinationof: means for applying a counterbalancing force to a moving part of saidapparatus for counterbalancing the reciprocating parts thereof, saidmeans including a fluid-tight chamber containing gas under pressure, anda piston closing said chamber and connected to a moving part of saidapparatus in such manner that said gas is expandedand energy isdelivered to said piston during the pumping stroke of said plunger andthe gas is compressed by said piston during the return stroke of saidplunger; means for increasing the pressure of said gas; means fordecreasing the pressure of said gas; and means responsive to thedifference in loads on a moving part of said apparatus during'thepumping and return strokes of said plunger and acting during a portionof each pumping cycle, said last mentioned means being adapted uponrelative increase in load during the pumping stroke to bring intooperation said means for increasing the pressure of said gas, andadapted upon relative decrease in load during the pumping stroke tobring into operation said means for decreasing the pressure of said gas.

9. In apparatus for reciprocating a. pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke, including amember operatively connected with said plunger, a prime mover, and asecond member driven by said prime mover, the combination of: meansconnecting said members for reciprocation o! said plimger, said meanscomprising a cylinder connected to one of said members and containingfluid, a piston in said cylinder connected to the other of said membersand dividing said cylinder into two fluid compartments, and a restrictediluid connection between said two compartments, whereby said pistonreciprocates in said cylinder coincidentally with the reclprocation ofsaid plunger; means for applying a counterbalancing force to a. movingpart of said apparatus for counterbalancing the reciprocating partsthereof; and means acting during a portion of each pumping cycle toincrease said counterbalancing force when the length ot stroke of saidpiston'- occurring during the pumping stroke of said plunger is greaterthan the oppositely directed stroke of said piston occurring during thereturn stroke of said plunger,` and acting to decrease saidcounterbalancing force when the ilrst Y mentioned stroke ci said pistonis less than the lisv last mentioned stroke oi' said piston.

10. In an apparatus for reciprocating a pump plunger throughout apumping cycle comprising a pumping stroke and a return stroke, includinga rotating crank, a walking beam, a pitman connected to said crank, andmeans extending from said walking beam to said pump plunger wherebyrocking of said walking beam causes' compartments, whereby the length ofsaid connecting means is varied coincidentally with reciprocation ofsaid pump plunger-:a chamber containing gas under pressure; `a pistonclosing said chamber and connected to said walking beam in such mannerthat said gas is` expanded and:

energy is delivered to saidwalking beam during the pumping stroke ofsaid lplunger and the gas is compressed by said piston during .thereturn stroke of said plunger; a reservoir contain-V ing gas underpressure higher than the pres'- sure of gas in said chamber; avalvefadaptedto admit gas from said reservoir into said chamber when thepressure in said chamber is below Van equilibrium pressure; a valveadapted to -exhaust l gas from said chamber when the pressure in saidchamber is -above an equilibrium pressure; and

means acting to increase the equilibrium pres-A sures of said valveswhenthe change in length of said connecting means occurring during-thepumping stroke of said plunger is greater than that occurring during thereturn stroke of said plunger, and acting to decrease the equilibriumpressures of said valves when the change inlength of saidconnectin'gmeans occurring during the "pumping stroke of said plunger is less thanthat occurring during the return Astroke of said plunger.

ll. In an apparatus for reciprocating a pump plunger in a well includinga rotating crank, a

pitman connected to said crank` 'a walking beam, and means extendingfrom said walking .beamto said pump plunger whereby rocking of saidwalking beam causes reciprocation of said pump plunger, the combination-of 'a vcylinder connected to said walking beam and containing fluid; apiston in said cylinder dividing said cylinder into ,twov fluidcompartments; a iluid-connection between said two compartments;adjustable iiow restricting means in said iiuid connection; a chambercontaining-gas under pressure; apiston closing said chamber andconnected to said walking beam in suchv manner that said gas is expanded'and energy is delivered to said walking beam during the pumping strokeof said plunger and the gas is compressed by said piston during thereturn stroke of said plunger; a reservoir containing gas under pressurehigher than the pressure of gas in said chamber; a valve adapted toadmit gas from saidV reservoir into said chamber when the pressure insaid chamber is below anequilibrium pressure; a valve adapted 1 1 toexhaust gas from said chamber when the pressure insaid chamber is abovean equilibrium pressure; and means responsive to a shift in po sition ofsaid piston insaid cylinder acting to adjustv said valves to higherequilibrium pressures when said piston shifts upward in said cylinder,

and acting to adjust said valves to lower-equilibrif um pressures whensaid piston shirts downward in said cylinder.

12. In apparatus for reciprocatinga pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke including a memberoperatively connected with said plunger, a prime mover. and a secondmember driven by said primeLmover, the combination of: means .connectingsaid members for reciprocation of said plunger, said means comprising acylinder connectedpto one .of said members and containz in g fluid, avpiston in said cylindcr'dividing said .cylinder into two uidcompartments, and a restricted fluid connection between saidcompartments; a chamber containing gas under pressure; a piston closingsaid chamber andconnected to a moving part ofsaid apparatus in suchmanner thatl said gas is expanded'and energy is delivered to' saidpiston during the pumping stroke of said plunger and the gas iscompressed by said piston duringthe return strok'e of said plungerravariable-clearance compressor adapted to discharge gas into saidchamber; a valve adapted to exhaust gas from said 'chamber when thepressure in said chamber is greater than an crease the clearance ofsaid, compressor and to 'increase the equilibrium pressure of said valvewhen the length of stroke of said pistonoccurring during the pumpingstroke vof said plunger of said plunger, and acting to increase theclearance of said compressorA and to decrease the equilibrium'pressureof said valve when the iirst 'cquilibrium pressure; and means-acting t'odev mentioned stroke of said piston is less than the last mentionedstroke of said piston.

13. Inapparatus for reciprocating' a pump plunger in a well including a.rotating crank, a pitman connected to said crank, a walking beam,

and meansextending from said walking beam to said pump. plunger 'wherebyrocking of said Walking beam causes reciprocation of said pump plunger,the combination of: means of variable length connecting said pitman withsaid walking beam for rocking said. walking beam and com prisin'g acylinder containing uid, a pistonin said cylinder dividing said cylinderinto two compartments, and a restricted uid connection between said twocompartments, whereby the length of said connecting means is variedcoincidentally with reciprocation of said pump plunger; a chambercontaining gas under pressure; a

piston closing said chamber and connected to said walking beam in such amanner that said gas is expanded and energy is delivered to said Walkingbeam during the pumping stroke of said plunger andthe gas is compressedby said piston to said walking-beamwhereby rocking of saidV y walkingbeam causes reciprocation of said compresser piston and compression ofthe gas withinv said compressor tov a pressure determined by the llengthof said'connecting means, the discharge pressure. of said compressorincreasing .with shortening length of said connecting means;

beam to said pump plungerwhereby rocking of 'said 'walkingbearrc'auss"reciprocation of saidy `sure of said valve.

le. in apparatus for reciprocating a pump plunger in a well including arotating crank,

'a pitman connected to said crank, a walking beam, and means extendingfrom said walking pump plunger, the combination of an arm pivoted atspaced points to said pitman and to said walking beam; spring meansresisting movement of said arm in either direction from a centralposition; a chamber containing gas under pressure; a piston closing saidchamber and connected to saidwalking beam in such manner that said gasis expanded and energy is delivered to said walking beam during thepumping stroke of said plunger and the gas is compressed by said pistonduring the return stroke of said plunger; a reservoir containing gasunder pressure higher than that in said chamber; a valve adapted toadmit gas from said reservoir into said chamber when the pressure insaid chamber is l less than an equilibrium pressure; a valve adaptn edto exhaust gas from said chamber when the t pressure in said chamber isgreater than an equilibrium pressure; a movable member; a second movablemember; means engageable with :said arm adapted to move said rst movablemember when said arm moves upward beyond said central position; meansengageable with said arm adapted to move said second movable member whensaid arm moves downward beyond said central position; and meansresponsive to the differential movement of said iirst and second movablemembers acting to readjust the equilibrium pressures of said valves insuch manner that the equilibrium pressures are increased when the forceexerted by said pitman is greater during its upward .stroke than duringits downward stroke and said equilibrium pressures are decreased whenthe force exerted by said pitman is less during its upward stroke thanduring its downward stroke.

15. In apparatus for reciprocating a pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke including a motivepower source adapted to drive said pump plunger, the combination of:means for applying a counterbalancing force to a moving part of saidapparatus for counterbalancing the reciprocating parts thereof, saidmeans including a chamber containing gas under pressure, and a pistonclosing said chamber and connected to a moving part of said apparatus insuch manner that said gas is expanded and energy is delivered to saidpiston during the pumping stroke of said plunger and the gas iscompressed by said piston during the return stroke of said plunger;means for increasing the pressure of said gas; means for decreasing thepressure of said gas; a movable member; a second member movableindependently of said rst member; means responsive tothe maximum torqueof said motive power source during the pumping stroke of said plungeracting to move said rst movable member, and responsive to the maximumtorque of said motive power source during the return` stroke of saidplunger acting to move said secaioasie a valve adapted to exhaust gasfrom said cham# ond movable member; and means responsive to thedifferential movement or" said movable memu bers acting to bring intooperation said means for increasing the pressure of said gas when themovement of said first member is greater than the movement of saidsecond member, and acting to bring into operation said means fordecreasing the pressure of said gas when the movement of said nrstmember is less than the movement of said. second member.

16. In apparatus for reciprocating a pump plunger throughout a pumpingcycle comprising a pumping stroke and a return stroke including a motivepower'sourcesadaptedA toffdrive--ss'aid plunger, the combinationof:vmeansior applying a counterbalancing force to 1a moving part of saidapparatus for counterbalancing the reciprocating-parts thereof, saidmeans including a chamber containing gas under pressure, and a pistonclosing said chamber and connected to a moving part of said apparatus insuch manner that said gas is expanded anci energy is delivered to said-piston during the pumping stroke of said plunger and the gas iscompressed by said piston during the return stroke of said plunger; areservoir containing gas under pressure higher than that in saidchamber; a valve adapted to admit gas from said reservoir into saidchamber when the pressure in said chamber is less than an equilibriumpressure; a valve adapted to exhaust gas from said chamber when thepressure in said chamber is greater than an equilibrium pressure;

a first movable member; a second member movi iirst movable member isless than that of saidA second movable member; means in engagement withsaid first movable member for moving it in one direction; means inengagement with said second movable member for moving it in a directionopposite to said iirst mentioned direction; means for pivotallysupporting the frame of said motive power source; resilient' meansresisting rotation of said frame of the motive power source; meansconnected to said frame of the motive power source, said means beingadaptedat the time of maximum torque of said motive power source duringthe pumping stroke of said plunger to engage said means in engagementwith said nrst movable member, whereby said rst movable member is movedby an amount correspondingto said torque then existing, and beingadapted at the time of maximum torque of said motive power sourceduringthe return stroke of said plunger to engage said means inengagement with said second movable member, whereby said second movablemember is moved by an amount corresponding to said torque then existing;and means returning said means in engagement with said rst and secondmov,- able members to denite positions in the path of said meansconnected to said frame.

17. The method of automatically counterbalancing the reciprocating partsof a. pumping apparatus ln which a. pump plunger is reciprocatedthroughout a. pumping cycle consisting of a pumping stroke and a returnstroke, comprising: applying a counterbalancing force to a. movingportion to the diierence in said forces exerted during the twooppositely directed strokes ofsaid plunger to make saidforces equal.

18. 'I'he method of automatically counterbalancing -the reciprocatingparts of a pumping ap' paratus in which a pump plunger is reciprocatedthroughout a pumping cycle consisting of -a pumping stroke and a returnstroke, comprising: applying a counterbalancing force to a moving partof said apparatus; measuring the force required to be exerted by amoving part of said apparatus during each pumping stroke of said er forreciprocation thereof, comprising: com,

pressing a gas on the downward stroke'of said plunger and expanding saidgas on the upward stroke of said plunger, whereby a counterbalancingforce is applied to a moving part of said apparatus; measuring the forceexerted by said pitman on said walking beam during each upward stroke'ofsaid plunger; measuring the force exerted by said pitman during eachdownward stroke of said plunger; and readjusting the pressure of saidgas in proportion to the diiference in said forces exerted during saidoppositelyfdirected strokes in such a direction as to make said forcesmore nearly equal.

20. In an apparatus for reciprocating a member through a power strokeand a return stroke, and including a driving element, the combinationof: adjustable means for applying a counterbalancing force to a movingpart of said apparatus for counterbalancing the reciprocating partsthereof, whereby theloads on said driving element during the power andreturn strokes of said member are substantially equalized; means movablein response to preponderance of the load on said driving element duringone of said strokes over the load on the driving element during theother of said strokes; and means operatively connecting said responsivemeans with said counterbalancing means to adjust said counterbalancingmeansfor reduction of said preponderance, whereby substantialequalization of the loads on said two strokes is maintained withchanging magnitude of the load on the power stroke.

21. In an apparatus for reciprocating a member through a power strokeand a return stroke, and including a drivingelement, the combination of:adjustable means for applying a counterbalancing force to a moving partof said apparatus for counterbalancing the reciprocating lparts thereof,whereby the loads on said driving element during the power and returnstrokes of said member are substantially equalized; and means toindicate adjustment of said counterbalancing means required to maintainsaid substantial equalization of loads, said indicating means beingadapted to move from a normal neutral position in response topreponderance of the loadV on said driving element during one of saidstrokes over the load on the driving element during the other of saidstrokes.

'22. The method of automatically counterbalancing the reciprocatingparts of an apparatus in which a prime mover reciprocates a workingmember throughout acycle consisting of a working stroke and a returnstroke, and in which some means responds to the load imposed on theprime mover, said method including the steps of: applying acounterbalancing force to a moving part of said apparatus; measuring theresponse of said means to the loads imposed on the prime mover on theworking strokes of the apparatus; measuring the response of said meansto the loads imposed on the prime mover on the return strokes of theapparatus; and readjusting said soA` counterbalancing means inproportion to the dierence in said responses on the two opposite strokesof the apparatus to make said responses substantially equal.

- WALTER E. SAXE.

